The present invention relates to a method for connecting a semiconductor device to a terminal electrode portion on a circuit board to mount the semiconductor device, and more particularly, to a method for forming a bump by using the laser ablation method which is a processing method where an interatomic bond or an intermolecular bond is severed by excitation caused by the energy of a laser and the severed atoms and atomic groups or molecules and molecular groups are transported by the energy of the laser. Moreover, the present invention relates to a method for encapsulating the semiconductor device and the circuit board in resin by the laser ablation method.
In accordance with a conventional method for connecting a semiconductor device to a terminal electrode portion on a circuit board to mount the semiconductor device, as shown in the cross-sectional view of a principal portion in FIG. 5, first, bump electrodes 7 of an alloy such as solder are provided on electrode pad portions 6A of a semiconductor device 6. The bump electrodes 7 are electrically connected to terminal electrode portions 8 on a circuit board 9 through a conductive adhesive containing a conductive filler made of an alloy of two or more kinds of metals.
In order to reply to demand of miniaturization of the semiconductor device 6, it is necessary to reduce the bump electrodes 7 in size. However, according to the conventional mounting method of the semiconductor device 6, the lower limit of the diameter of the bump electrode 7 is approximately 80 .mu.m, and it is difficult to further reduce the diameter.
In addition, when the conductive adhesive containing the conductive filler made of an alloy of two or more kinds of metals is used for electrically connecting the bump electrodes 7 to the terminal electrode portions 8 on the circuit board 9, it takes two or more hours to set the adhesive, which renders this method disadvantageous in processing speed.
In another method, the bump electrodes 7 is soldered to the terminal electrode portions 8 of the circuit board 9 by the reflow soldering process. This process can be made quickly. The circuit board 9 having the semiconductor device 6 is encapsulated by epoxy sealant in the next step, and a resin-encapsulated portion is formed. However this process takes two to four hours to set the epoxy sealant. Since such a long time is necessary, a great difference in cycle time occurs in the production line, and therefore this method cannot be matched the mounting method according to SMT (surface mount technology).
An object of the present invention is to solve the above-mentioned problems associated with the mounting of a semiconductor device on a circuit board, not by the method using an adhesive or an epoxy sealant but by the laser ablation method.